1. Field of the Invention
The present invention relates generally to the field of loudspeaker design and specifically to the design of more efficient loudspeakers for long-term outdoor use.
2. Background of the Invention
As loudspeakers designed for outdoor use have become more popular the demand for improved performance for this application has also increased. A particular problem for loudspeakers used outdoors is reproduction of adequate quantity and quality of low frequency sounds. For indoor applications, the enclosed nature of the room where the loudspeaker is located contributes to increased low frequency response and efficiency, known as “room gain”. In contrast, outdoor applications do not have the benefit of any such “room gain” at low frequencies and are, therefore, disadvantaged in regard to both low frequency response and efficiency. Furthermore, for indoor applications, one of the most common techniques to obtain greater low frequency efficiency is the use of a ported enclosure. Those skilled in the art will confirm that that the use of a port or vent, sometimes also referred to as a duct, in a loudspeaker enclosure can produce significant gains in efficiency at low frequencies as compared to a sealed enclosure. However, this technique is rarely used in loudspeakers designed for long-term outdoor use due to the need for weather resistance in a variety of orientations and the need to keep debris, insects and other vermin from entering the loudspeaker enclosure. Occasionally, ports are used in outdoor loudspeakers with a screen or mesh covering the port opening. However, while effective in preventing debris and insects from entering the enclosure, this approach does little to keep out water and substantially diminishes performance due to the turbulence and loss generated by the screen. In general, loudspeakers designed for long-term outdoor use employ sealed enclosures which typically offer lower efficiency at low frequencies and further reduce the ability of such outdoor loudspeakers to reproduce adequate quantity and quality of low frequency sounds.
Therefore, needed in the art is a porting structure which is sufficiently resistant to intrusion by water, debris, insects and other vermin so as to be acceptable for most outdoor applications regardless of the orientation of the loudspeaker system and the port structure while still being compact, efficient and reducing turbulence and loss.